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// Other services

Port 773:

Port 773 is assigned by IANA to notify (), submit ().

773

How notify works

Other services
client:773notifyresponse client:773notifyresponse

The client sends a request to port 773 and the notify service answers.

Transport
UDP · TCP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned2 registered services
Range
Well-known (0-1023)
Category
Other services
01 Security

Is port 773 dangerous?

We have no specific security note for port 773. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 773

ServicePortTransportDescriptionReferenceUpdated
notify 773 UDP - -
submit 773 TCP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 773, and is it reachable?

Linux

sudo ss -ltnup 'sport = :773'      # process listening on 773
sudo lsof -nP -i :773

macOS

sudo lsof -nP -i :773

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 773 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 773
netstat -ano | findstr :773

From another machine

nmap -p 773 -sV <host>
sudo nmap -sU -p 773 <host>
nc -zv <host> 773

Block it in the firewall

sudo ufw deny 773/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 773" -Direction Inbound -LocalPort 773 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 773 used for?

Port 773 is assigned by IANA to notify (), submit ().

Is port 773 TCP or UDP?

Port 773 is registered for UDP and TCP.

Is it safe to open port 773?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.

How do I check if port 773 is open?

On Linux run "ss -ltnup 'sport = :773'", on macOS "lsof -nP -i :773", and on Windows "netstat -ano | findstr :773" to see the local process. From another machine, "nmap -p 773 <host>" shows whether it is reachable.

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